For purposes of the present invention, a filament is a slender body whose transverse dimensions are much less than its length. In that context, filaments may be bodies such as ribbons, strips, sheets or wires, of regular or irregular cross section. As used herein, an "amorphous filament" is a filament of a metal alloy having amorphorus molecular structure.
It is known to make metal filaments by directing a jet of molten metal against a rotating quench surface, or by otherwise depositing molten metal on such quench surface, whereon it is solidified in the form of a ribbon and is flung away by action of centrifugal force, as for example described by Strange and Pim in U.S. Pat. No. 905,758. In the procedure described by Strange and Pim the quench surface is furnished by a rotating chill roll. That procedure is suitable to form filaments of many of the polycrystalline metals which possess sharp melting points, that is to say, which have solid-liquid transition range of less than about 4.degree. C. However, glassy metals having amorphous molecular structure often have a transition range in the order of about 400.degree. C. or more through which the viscosity of the metal gradually increases until the critical glass transition temperature is reached, and it is necessary for the filament to be quenched below its glass transition temperature before departure from the quench surface. This is difficult to achieve by the procedure of Strange and Pim because centrifugal action tends prematurely to fling the filament away from the chill roll. Also, in that procedure the point of release of the filament from the surface of the chill roll varies, so that it is difficult to collect the filament and to guide it to a suitable winder.
Shortcomings concerning insufficiency of retention time of filament on the surface of the chill roll, and difficulties in collecting the filament from a variable point of release, are overcome by the procedures described by Kavesh in U.S. Pat. No. 3,856,074 and Bedell in U.S. Pat. No. 3,862,658. The Kavesh procedure involves retention of filaments formed on the exterior surface of a rotating chill roll by use of nipping means; the Bedell procedure involves prolonging the period of contact between the filament and the chill roll by exerting a force against the surface of the chill roll in the direction towards the axis of rotation of the chill roll by devices such as gas jets, moving metal belts and rotating wheels. In a specific embodiment Bedell employs a metal belt of beryllium copper running over two rollers for confining the ribbon to prevent early separation from the chill roll. However, use of two rollers imposes geometrical and practical limitations as to the angle over which the ribbon can be urged against the rotating chill roll, and when the contact angle of the ribbon with the roll is small, a wavy ribbon may result. Moreover, use of a metal belt inherently involves danger of damaging the highly sensitive surface of the chill roll, as by marring it because of solid-to-solid contact between the surface of the chill roll and the relatively rigid, and relatively hard metal belt. The slightest imperfection in the surface of the chill roll will be noticeable on the surface of the filament formed, resulting in a product of inferior appearance. Furthermore, unless the belt is narrower than the filament, or at least not wider than the filament, then the belt will be subject to severe buckling, as the section in contact with the hot filament will undergo thermal expansion, whereas the marginal portions not in contact with the filament will not undergo such expansion. However, unless the belt is wider than the filament, the marginal portions of the filament will tend to be unevenly quenched, resulting in filament having uneven properties.
Wheel-and-band type metal casting machines for continuous casting of metallic strip wherein molten metal is deposited into the cavity formed between a grooved casting wheel and a metal retaining band moving together with the casting wheel have been known for some time. Such machines may employ a multiplicity of guide and/or driving wheels for the metal band. For example F. A. Feldkamp et al. in U.S. Pat. No. 1,220,211 disclose such a wheel and band type casting machine. Feldkamp et al.'s apparatus employs a casting wheel having a series of equidistant studs or cores protruding into the casting cavity to provide perforated strip product.